Taste Sensitivity to 6-N-Propylthiouracil (PROP) as a Biological Marker for Vulnerability to Stress in Mothers and Children

Some people are genetically more vulnerable to stress than others, leading them towards poorer outcomes following stressful events. Mothers' vulnerability to stress may, in turn, influence their children, leading their children towards poor outcomes as well. A biological marker of vulnerability to stress may indicate mothers who are at greater risk for experiencing parenting stress, depression, and less support of the infant's emotional development, and infants who are at greater risk for development of poor emotion regulation and behavior problems. Taste sensitivity to propylthiouracil (PROP) is proposed as a biological marker of stress vulnerability in mothers and children. This research used a bioecological approach to examine extant data from two previous longitudinal studies, both with child and mother data from maternal interviews and video-recorded observations of mother-child interaction. Participants included 121 low-income and 102 middle-income mother-child pairs who were studied for presence of the biological marker in relation to stressful life events, parenting stress, depression, and lower support of infants' emotions. Children were studied for presence of the biological marker in relation to their development of emotion regulation and their later behavior problems.Results revealed that PROP taste sensitivity, as tested in this study, is not likely to be a useful biological marker of higher vulnerability to stress. Although results flowed in the hypothesized direction, few reached statistical significance and most were of small effect size. For depression, results supported previous research, although with smaller effect sizes. In addition, results depended on the sample and source of stress. For low-income mothers the source of stress was stressful life events. For the middle-income sample the source of stress was parenting stress, specifically mother-child dysfunctional interaction. Among mothers with higher PROP taste sensitivity, those from the low-income sample reported more depression whether stressful events were higher or lower, whereas those from the middle-income sample reported more depression when parenting stress, particularly poor mother-child dyadic interaction, was higher. From both samples, mothers' parenting stress or depression at 14 months predicted children's later behavior problems when they were school-age. Children with lower PROP taste sensitivity were more emotionally regulated with their mothers. Because the results were consistent and suggestive, although not conclusive enough to warrant the use of PROP as a biological marker, future research should examine individual situational factors under which PROP taste sensitivity is related to stress vulnerability.